Initialise mid_q_entry before putting it on the pending queue

A user reported a crash in cifs_demultiplex_thread() caused by an
incorrectly set mid_q_entry->callback() function. It appears that the
callback assignment made in cifs_call_async() was not flushed back to
memory suggesting that a memory barrier was required here. Changing the
code to make sure that the mid_q_entry structure was completely
initialised before it was added to the pending queue fixes the problem.

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 14 insertions, 12 deletions

diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 3097ee58fd7d..f25d4ea14be4 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -365,16 +365,14 @@ cifs_setup_async_request(struct TCP_Server_Info *server, struct kvec *iov,
         if (mid == NULL)
                 return -ENOMEM;
 
-        /* put it on the pending_mid_q */
-        spin_lock(&GlobalMid_Lock);
-        list_add_tail(&mid->qhead, &server->pending_mid_q);
-        spin_unlock(&GlobalMid_Lock);
-
         rc = cifs_sign_smb2(iov, nvec, server, &mid->sequence_number);
-        if (rc)
-                delete_mid(mid);
+        if (rc) {
+                DeleteMidQEntry(mid);
+                return rc;
+        }
+
         *ret_mid = mid;
-        return rc;
+        return 0;
 }
 
 /*
@@ -407,17 +405,21 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
         mid->callback_data = cbdata;
         mid->mid_state = MID_REQUEST_SUBMITTED;
 
+        /* put it on the pending_mid_q */
+        spin_lock(&GlobalMid_Lock);
+        list_add_tail(&mid->qhead, &server->pending_mid_q);
+        spin_unlock(&GlobalMid_Lock);
+
+
         cifs_in_send_inc(server);
         rc = smb_sendv(server, iov, nvec);
         cifs_in_send_dec(server);
         cifs_save_when_sent(mid);
         mutex_unlock(&server->srv_mutex);
 
-        if (rc)
-                goto out_err;
+        if (rc == 0)
+                return 0;
 
-        return rc;
-out_err:
         delete_mid(mid);
         add_credits(server, 1);
         wake_up(&server->request_q);